Mosquitoes are arguably the most medically important group of insects. In addition to causing severe annoyance and allergic reaction, mosquitoes found in California are capable of spreading many diseases to humans and animals including:
Historically, California has experience local transmission of malaria, western equine encephalomyelitis (WEE), St.Louis encephalitis (SLE), California encephalitis viruses, canine heartworm, and West Nile virus (WNV). Canine heartworm and West Nile virus continue to have frequent local transmission in California with West Nile virus human cases numbering in the hundreds every year. However, with increased global travel, the potential for the introduction or reintroduction of many mosquito-borne diseases into California exists.